Subsurface Equipment/Artificial Lift

Maximizing Production from the Well

“In October, 1859, Colonel Edwin Drake rigged up a pump to produce an oil and water mixture a distance of ten feet to the surface. It was the world’s first commercial oil well and the first use of artificial lift to commercially produce oil.” Today, 140 years later, pumps are employed in more than 80% of all artificial-lift wells.

When oil or gas is being produced the reservoir pressure reduces. At a certain point in time it can happen that the pressure in the reservoir becomes too low for production and artificial lift can be required. Artificial-lift methods fall into two groups, those that use pumps and those that use gas.

Beam Pumping

The walking beam pump, was an idea borrowed from the water-well industry. One end of a heavy wooden “walking beam” set on a pivot was attached by a stiff rod to a steam engine. Attached to the other end of the beam was a string of long, slender “sucker rods,” which were connected to a pump at the bottom of the well. The engine cranked the rod up and down and actuated the pump to pump oil to the surface. Since the introduction in 1925 the Trout-designed pumps have become the dominant artificial-lift beam-pumping unit. Over the years developments focused on improvement of the reliability of the pump parts and design methods. For example the sucker rod material changed from wood to fiber glass steel and plastic reinforced. The design methods were significantly improved by the Gibbs’ sucker-rod diagnostic technique. “The technique uses mathematical equations to model the elastic behavior of long sucker rod strings,” says Gibbs.

Electrical Submergible Pumps (ESPs)

The first electrical submergible pumping unit was developed in Russia in 1917 by Armias, who later migrated to California. Although initially not very successful, the use of ESPs in the oil industry was assured by the help of Frank Phillips of Phillips Petroleum Co. in Bartlesville, Oklahoma. Since that time, the concept has proved to be an effective and economical means of lifting large volumes of fluid from great depths under a variety of well conditions. Today’s ESPs are essentially multistage centrifugal pumps that employ blades, or impellers, attached to a long shaft. The shaft is connected to an electrical motor that is submerged in the well. The pump usually is installed in the tubing just below the fluid level, and electricity is supplied through a special heavy-duty armored cable.

Subsurface Hydraulic Pumps

There are two types of hydraulic pumps for artificial lift. One is fixed-pump design; the other is free-pump design. In fixed installations, the downhole pump is attached to the end of the tubing string and run into the well. Power fluid is directed down an inner tubing string, and the produced fluid and the return power fluid flow to the surface inside the annulus between the two tubing strings. Free-pump installations allow the downhole pump to be circulated into and out of the well inside the power-fluid tubing string, or they can be installed and retrieved by wireline operations. Jet pumps are a special class of hydraulic subsurface pumps and are sometimes used in place of reciprocating pumps. Unlike reciprocating pumps, jet pumps have no moving parts and achieve their pumping action by means of momentum transfer between the power fluid and produced fluid.

Gas Lift

This method artificially injects gas in the well through gas lift valves. The gas reduces the weight of the liquid column which in a reduction of bottomhole pressure. The effect is an increase of liquid production. Since its development in the 1930s, several important developments took place. Modern gas lift installations have valves that can easily be retrieved installed in side pocket mandrels.

The Future

Artificial-lift technologies of the future will involve software, electronics, sensor technologies and data transfer and data management. This will require an effort of developers to explore the limits of technology.

References

Brown, K., Day, J., Byrd, J., and Mach, J.: The Technology of Artificial Lift Methods, Vol. 2a, Petroleum Publishing Co., Tulsa (1980) 2.
Knowles, R.S.: The First Pictorial History of the American Oil and Gas Industry 1859-1983, Ohio U. Press, Athens, Ohio (1983) 7.
Day, J. and Byrd, J.: “Beam Pumping: Design and Analysis,” The Technology of Artificial Lift Methods, Vol. 2a, Petroleum Publishing Co., Tulsa (1980) 9.
Fundamentals of Petroleum, third edition, Petroleum Extension Service, U. of Texas, Austin (1986) 179.
Lufkin Industries Inc., http://www.lufkin.com/pump.html
Day, J. and Byrd, J.: “Beam Pumping: Design and Analysis,” The Technology of Artificial Lift Methods, Vol. 2a, Petroleum Publishing Co., Tulsa (1980) 9.
EVI Oil Tools Inc., http://www.weatherford.com.
Brown, K., Day, J., Byrd, J., and Mach, J.: The Technology of Artificial Lift Methods, Vol. 2a, Petroleum Publishing Co., Tulsa (1980) 80.
Bradley, H.B.: Petroleum Engineering Handbook, third printing, SPE, Dallas (1992) 5–12.
“Artificial Lift,” Weatherford “W,” Weatherford Intl. Inc. (winter 1999) 23.